1. Field of the Invention
The invention relates to a method and apparatus for cooling hot gases and fluidized slag in entrained flow gasification. The method is suited for a reactor for entrained flow gasification and for cooling the gasifying gas heated to a temperature ranging from 1,200 to 1,800° C., using pressures of up to 80 bar. The hot gasifying gas and the liquid slag exit these reactors together for entrained flow gasification of solid and liquid combustibles, and enter the cooling chamber, which is also often referred to as the quench chamber, with gasification being performed as an autothermal partial oxidation. The combustible may be pressurized as a carbon-water or carbon-oil suspension, a so-called slurry, or pneumatically as dry combustible dust and supplied to the reactor's head via burners for gasification. One or more combustibles or carbon types can be gasified.
2. The Prior Art
In gas production technique, the autothermal entrained flow gasification of solid, liquid and gaseous combustibles has been known for many years. For reasons of synthesis gas quality, the ratio of combustible to oxygen-containing gasification agents is chosen such that higher carbon compounds are completely cleaved into synthesis gas components such as CO and H2 and the inorganic constituents are discharged in the form of a molten slag.
According to different systems well known in the art, gasifying gas and molten slag can be discharged separately or together from the reaction chamber of the gasification apparatus, as described for example in German Patent No. DE 197 18 131 A1.
German Patent No. DE 3534015 A1 shows a method in which the gasification fluids, small coal and oxygen-containing oxidizing agents are introduced into the reaction chamber via a plurality of burners in such a manner that the flames cause each other to deviate. Thereby, the gasifying gas flows upward, loaded with particulate matter, and the slag flows downward into a slag cooling system. Usually, an apparatus for indirect cooling using waste heat is provided above the gasification chamber. The entrained liquid slag particles however are likely to deposit and coat the heat exchanger surfaces, with the heat transfer being impaired and the tube system possibly becoming clogged or erosion occurring as a result thereof. The risk of clogging is countered by cooling the hot crude gas with a circulated cooling gas. The slag exits the gasifier and directly enters a waste heat vessel in which the crude gas and the slag are cooled for vapor generation, using waste heat. The slag accumulates in a water bath and the cooled crude gas exits the waste heat vessel sideways. The advantage of this waste heat production according to this system is offset by a series of disadvantages, in particular, the formation of deposits on the heat exchanger tubes, which impair heat transfer and lead to corrosion and erosion and, as a result thereof to a lack of availability.